Final answer:
The event AUB represents the combination of all outcomes in events A and/or B. For the dice example, event AUB has five outcomes: {1, 2, 3, 4, 6}.
Step-by-step explanation:
To describe the event AUB, we must understand that this event includes all outcomes that are in event A, event B, or in both A and B. Considering the definitions provided, if we let event A be the set of outcomes where an even number is rolled, and event B be the set where a number less than four is rolled, then AUB contains all those outcomes that are either even numbers or numbers less than four or both. Since we know that the even numbers less than four are 2, and considering a six-sided die, the event A could be {2, 4, 6}, and event B could be {1, 2, 3}. Therefore, AUB would be {1, 2, 3, 4, 6}. To find the number of outcomes in the event AUB, we just count the number of elements in this set, which would be five outcomes.